I hate L/HaRGB!

[Astrosurf]

I'm putting this in the beginner's section as I'm still struggling with L/HaRGB. I hate it. I can never get it right and it needs so much faffing about. The images are never clean. I'm going back to my DSLR for colour! Here's my M108. 'Could do better' is what my report would say! I'll have another go with the DSLR and see how it compares. I know it'll be a much larger FOV, but I'm curious.

Alexxx

 

[kens]

Is this a request for help or a general rant?

If a request for help then more info is needed. How many subs, length, what kind of filters, post-processing etc... An is there any specific aspect of the image that is botehring you?

Just looking at the jpeg your focus looks a bit soft.

[swag72]

My first thought when I saw this was that it was out of focus....... While in my experience (I dislike HaLRGB immensely too!) you can get away with a softer RGB base, the luminance channel has got to be bang on the money.

The background looks clean..... no noise

[JohnSadlerAstro]

Hi,

Could it be Ha causing star bloating? I'm not sure there would really be much Ha signal in a galaxy, anyway?

John

[ollypenrice]

Whoa,  LRGB is beautiful!

It is so straightforward then even I can do it - and I'm only a man! I must admit, though, that Pixinsight's DBE does make it much easier. The procedure:

1 Capture equal amounts of R, G and B. Stack and calibrate the captures as separate channels.

2 Co-register the three images so that they are aligned to each other.

3 Combine them in a suitable colour combining software. I use AstroArt for stacking and colour combining. You can try using AstroArrt's 'auto colour balance' but I don't do that. I combine at equal weighting, crop the edges and go into PI.

4 Run DBE in PI. This will give you a near perfect colour balance and neutral background sky for the rest of the project.

Alternative 4 if you don't have PI. Give the image a basic stretch in Ps and use Gradient Xterminator. Be sure to use it effectively by getting it to work on the background rather than the object.

5 In levels, while processing, keep an eye on the histogram peak in each channel. The top left of each histo peak should be aligned (as a rule of thumb, not a religion.) You can only adjust by moving the peaks to the left with the black point slider.

6 Keep an eye on your background sky values using the colour sampler eyedropper in Ps. I like my backgrounds to be about 23/23/23 in R/G/B. You can adjust this by using the colour balance tool set to shadows.

 

If you'd like to Dropbox me your three channels I'll gladly have a look. Or post a link up here.

Olly

Edit: You are not very far out at all with the image posted.

 

[Astrosurf]

Thanks all. A rant mainly but advice is always welcome! Always learning. The soft stars are as a result of the processing. I find it hard to stop even with vigorous deselection of stars when stretching. I did a lot of G blur on the background to remove noise and did a separate image thingy (my tech term!) to remove the persistent patchiness in the background. It was a windy night which caused trailing so I had to correct that too. Not the best image to start with but I hate being beaten. I'll give you the capture details later as I'm on my mobile and haven't got them to hand. 

[Astrosurf]

Thanks Olly! I did do the GXT but too late in the stretching so it caused probs. My bad! And I always check the histo peaks regularly throughout processing. I did the proper alignment using a ref image in DSS and assigned the RGB in channels. I wish I could afford PI but then I wouldn't understand it. (SpLD issues) still need dosh for Astroart!

All, this is an LRGB image. I just hate HaRGB too! 

[Peter Drew]

12 minutes ago, ollypenrice said:

Whoa,  LRGB is beautiful!

It is so straightforward then even I can do it - and I'm only a man! I must admit, though, that Pixinsight's DBE does make it much easier. The procedure:

1 Capture equal amounts of R, G and B. Stack and calibrate the captures as separate channels.

2 Co-register the three images so that they are aligned to each other.

3 Combine them in a suitable colour combining software. I use AstroArt for stacking and colour combining. You can try using AstroArrt's 'auto colour balance' but I don't do that. I combine at equal weighting, crop the edges and go into PI.

4 Run DBE in PI. This will give you a near perfect colour balance and neutral background sky for the rest of the project.

Alternative 4 if you don't have PI. Give the image a basic stretch in Ps and use Gradient Xterminator. Be sure to use it effectively by getting it to work on the background rather than the object.

5 In levels, while processing, keep an eye on the histogram peak in each channel. The top left of each histo peak should be aligned (as a rule of thumb, not a religion.) You can only adjust by moving the peaks to the left with the black point slider.

6 Keep an eye on your background sky values using the colour sampler eyedropper in Ps. I like my backgrounds to be about 23/23/23 in R/G/B. You can adjust this by using the colour balance tool set to shadows.

 

If you'd like to Dropbox me your three channels I'll gladly have a look. Or post a link up here.

Olly

Edit: You are not very far out at all with the image posted.

 

Blimey, if that's "ALL" you have to do to get a good picture then I can't believe I've not yet taken up imaging!  

[Astrosurf]

OK, so I took 8 x L subs at 5 mins. Then 4 each of RGB, 2x2 binning, at 2.5 mins. I don't use Dropbox as they keep telling me I've used all my free space and have to pay for there service, even though I've deleted most of the stuff! Here's a Google Drive link to the subs. They do have star trailing so I had to rotate the finished image so the trailing was horizontal then used Scale in PS to correct. I'm sure someone will recommend a better way!

https://drive.google.com/open?id=0ByORvfYYCt4Lbl9tVWpkRjBoVzg

[ollypenrice]

46 minutes ago, Peter Drew said:

Blimey, if that's "ALL" you have to do to get a good picture then I can't believe I've not yet taken up imaging!  

It's easier than grinding a mirror, Peter!

Olly

[ollypenrice]

39 minutes ago, Astrosurf said:

OK, so I took 8 x L subs at 5 mins. Then 4 each of RGB, 2x2 binning, at 2.5 mins. I don't use Dropbox as they keep telling me I've used all my free space and have to pay for there service, even though I've deleted most of the stuff! Here's a Google Drive link to the subs. They do have star trailing so I had to rotate the finished image so the trailing was horizontal then used Scale in PS to correct. I'm sure someone will recommend a better way!

https://drive.google.com/open?id=0ByORvfYYCt4Lbl9tVWpkRjBoVzg

Thanks Alex, I'll have a look. Meanwhile, on this thread (near the end), I ran the OP's data through DBE.

This is a perfect example of the incredible power of this routine when it comes to sorting out colour balance. Note that this is DSLR colour data so any image, however captured, does need the colour sorting.

Olly

[Astrosurf]

Thanks Olly. Oh, for the money!

[Peter Drew]

1 hour ago, ollypenrice said:

It's easier than grinding a mirror, Peter!

Olly

Maybe, but I know how to grind a mirror so the learning curve is flatter. 

[wimvb]

Alex,

I think you did rather well with the limited data you have. To get the noise down, you would really need more subs. There are also a few hot pixels that would benefit from either darks or a bad pixel map.

I played a little with your data. As you, I generally don't do LRGB processing, only DSLR. Below is the workflow I followed.

Used dbe to remove vignetting. Then deconvolution on the stars (there is a slight ringing effect around some smaller stars) (Lum data only). Used L*a*b mode for the colour work.

workflow, in PixInsight:

image registration and integration (percentile clipping)

rgb combination

cropping of rgb and luminance

dbe on rgb and luminance (division to remove vignetting effects)

Lum:

deconvolution

masked stretch and exponential stretch with lightness mask

HDRmultiscale transform to enhance detail in the galaxy

RGB:

masked stretch in 3 passes for rgb (this boosts colour, but keeps the contrast down)

extracted a and b components of L*a*b colourspace

 

L*a*b combination with a and b from rgb image, and Lum for L

Noise reduction: MulitscaleMedianTransform on chroma, TGVDenoise on L

contrast enhancement and slight star reduction using MorphologyTransform

 

L*a*b component extraction and recombination should be possible in PS as well.

 

Cheers,

[ollypenrice]

Good job from Wim!

Olly

[wimvb]

Thanks Olly.

Alex, eve if you don't have PixInsight, the key parts in my workflow were dbe and using Lab colour mode for combining the colour and L data. Since rgb already has luminance information in it, I find that combining it with more luminance, can give unpleasant results at times. In Lab mode, you completely separate luminance from colour data. To increase luminance data, you could even extract L from the rgb, and mix that with the luminance data. Then recombine this "super" L with the a and b components.

I hope you understand what I mean.

[SteveMcHarg]

That's a superb image well done ! 

[Astrosurf]

On 05/02/2017 at 00:32, wimvb said:

Alex,

I think you did rather well with the limited data you have. To get the noise down, you would really need more subs. There are also a few hot pixels that would benefit from either darks or a bad pixel map.

I played a little with your data. As you, I generally don't do LRGB processing, only DSLR. Below is the workflow I followed.

 

Used dbe to remove vignetting. Then deconvolution on the stars (there is a slight ringing effect around some smaller stars) (Lum data only). Used L*a*b mode for the colour work.

workflow, in PixInsight:

image registration and integration (percentile clipping)

rgb combination

cropping of rgb and luminance

dbe on rgb and luminance (division to remove vignetting effects)

Lum:

deconvolution

masked stretch and exponential stretch with lightness mask

HDRmultiscale transform to enhance detail in the galaxy

RGB:

masked stretch in 3 passes for rgb (this boosts colour, but keeps the contrast down)

extracted a and b components of L*a*b colourspace

 

L*a*b combination with a and b from rgb image, and Lum for L

Noise reduction: MulitscaleMedianTransform on chroma, TGVDenoise on L

contrast enhancement and slight star reduction using MorphologyTransform

 

L*a*b component extraction and recombination should be possible in PS as well.

 

Cheers,

That is soooo much cleaner than mine! Thank you for the info.

[Astrosurf]

On 05/02/2017 at 10:29, wimvb said:

Alex, eve if you don't have PixInsight, the key parts in my workflow were dbe and using Lab colour mode for combining the colour and L data. Since rgb already has luminance information in it, I find that combining it with more luminance, can give unpleasant results at times. In Lab mode, you completely separate luminance from colour data. To increase luminance data, you could even extract L from the rgb, and mix that with the luminance data. Then recombine this "super" L with the a and b components.

I hope you understand what I mean.

I don't really get it, but will have a cogitate! Many thanks.